Birds fly for only 10-20 m around a sanctuary.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/bird%E2%80%99s-eye-view-death-knell-sanctuary-say-environmentalists
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/indian-express-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/uttar-pradesh
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/okhala-sa
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/gautam-budha-nagar
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environmentalists
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/eco-sensitive-zone
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environment-act-1986
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ministry-environment-and-forests-moef
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/birds
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environment